Magenta couplers for use in commercial photographic materials, including films and papers, are usually drawn from the pyrazolone and pyrazolotriazole classes, in view of the stability of these compounds in raw-stock and their rapid and efficient reaction with oxidized color developers. Dyes derived from commercial pyrazolone and pyrazolotriazole magenta couplers also have acceptable spectrophotometric curve shapes.
Pyrazolone magenta couplers having secondary amino substituents in the 3-position have been used commercially. These couplers have been prepared via synthetic routes which involve acylation of the secondary amino group in the 3-position to form an amido protecting group, followed by removal of the N-acyl group to form the coupler materials; see e.g. JP-A-52/091862 which discloses the conversion of a nitro substituent of a phenyl ring on the 3-nitrogen atom to a tetradecanamide moiety, while the 3-secondary amino is protected by acylation (also see DE 2703589, DE 2651363).
U.S. Pat. No. 5,447,831 discloses the use of certain acyl compounds as ancillary couplers to the main image-dye forming couplers to improve printer compatibility, the couplers forming dyes having a peak absorption between 565-600 nm.
JP-A-58/117542 disloses N-acyl pyrazolones having a pentachiorophenyl substituent, which generate a dye having a peak absorption of 610 nm, giving improved color reproducibility.
U.S. Pat. No. 4,021,238 discloses fogged emulsion layers containing an N-phenyl-N-benzoyl pyrazolone that forms a nondiffusible colored dye with oxidized color developer, giving improved color reproduction and high sharpness.
JP-A-05/100388 discloses N-acyl pyrazolones which provide formaldehyde image stability, the compounds having a carbamate or ureide moiety attached to the pyrazolone ring.
DE Offenlegungschrift No 2018562 discloses pyrazolones substituted with an imide moiety, which provide improved viscosities of silver halide emulsions as compared with those containing commercial couplers.
A disadvantage which is associated with magenta couplers of the pyrazolone and pyrazolotriazole types which have hitherto been used commercially in the art, is that the azamethine dyes formed by the condensation of these couplers with oxidized arylamine developers are generally less stable to actinic light as compared with the dyes derived from commercial yellow and cyan couplers.
It is an object of the present invention therefore to provide elements containing image dye-forming couplers which form azamethine dyes that are more stable to exposure to actinic radiation as compared with known pyrazolone and pyrazolotriazole couplers, and which at the same time retain the advantageous properties of these classes of couplers.